The influence of air-gap conditions on the structure formation of lyocell fibers

The influence of an air gap on the formation of a filament spun from a solution of cellulose in N-methylmorpholine N-oxide was studied. A number of parameters were investigated, principally, air-gap length, temperature, and humidity and the water content in the polymer solution. Their effect on the draw-down profile and orientation of the filament in the air gap was determined and compared to the structure and properties of the resulting fibers. It is shown that all these parameters have a strong influence on the structure formation process. Depending on the combination of parameters used, the phenomenon of draw resonance may or may not be observed. The results indicate that the cooling of the filament is driven by two simultaneous processes. Modifying the parameters studied also causes significant changes to the resulting fiber properties, but the fiber structures, measured by birefringence and wide-angle X-ray diffraction, appear almost identical. (C) 1996 John Wiley & Sons, Inc.